Upper Three Runs Creek is a 20-mile (40-kilometer) waterway that meanders through hardwood and cypress forests on the 310-square- mile (806-square-kilometer) Savannah River Site near Aiken, S.C. It empties into the Savannah River. The creek is a blackwater stream because of its high concentration of naturally occurring tannic acid that gives the water its tea color. Scientists have recorded more than 575 species of aquatic insects in Upper Three Runs, probably giving it the second highest level of aquatic insect biodiversity in the world. Breitenback Creek in southern Germany contains a recorded 635 aquatic insect species. The next highest levels of aquatic insect biodiversity are found in tropical streams in Malaysia and Australia, but both have fewer than 400 species.
Though scientists have documented more than 575 species of aquatic insects in Upper Three Runs Creek, the figure does not include other species of invertebrates. These include round worms, crayfish, other large crustaceans and mussels. Altogether, the stream may contain as many as 700 invertebrate species.
Upper Three Runs is the only known locality of the blackbanded sunfish and the turquoise darter in the Savannah River drainage.
The bottomland area and adjacent valley slopes surrounding Upper Three Runs Creek are important habitats for plants. Eight plant species that are listed on federal and/or state lists of species of special status are found in this set-aside area. They are: sandhill seedbox, milk pea, bog spice bush, Nestronia, green- fringed orchid, Oconee azalea, spatulate seedbox and Chapman's sedge.
Scientists at Savannah River Ecology Laboratory believe Upper Three Runs Creek has such a high level of biodiversity because of a suite of unique characteristics working in concert. For one, Upper Three Runs is a spring-fed stream, which results in colder water temperatures. Thus, typically northern and mountain species of aquatic fauna coexist with the native southeastern species.
Researchers are using molecular biology techniques such as fatty acid analysis, physiological determinations, reverse genome probing and RNA sequencing, to learn more about the microbial communities that inhabit Upper Three Runs Creek. Microbes control most ecosystem level processes, such as nutrient and mineral cycling, which are necessary for the growth of other organisms. If scientists can determine that a habitat contains a healthy and diverse community of microbes, they can say it is a healthy environment. If there are only a few microbes present, an ecosystem's functions are limited. Waste products are not broken down; they accumulate in the environment.
Blackwater streams, such as Upper Three Runs Creek, are found throughout the southeastern United States. Many, however, suffer from pollution and siltation, which Upper Three Runs has only experienced at a minimum because of its location within the controlled access area of the U.S. Department of Energy's Savannah River Site. The stream also flows through a DOE- protected research set-aside area that cannot be developed for industry or forestry.
Did You Know?
This fact sheet was produced by the Outreach Program
of the Savannah River Ecology Laboratory.
Last review: October 12, 2007